bims-tunefa 2020-05-31 papers

bims-tunefa

Biomed News

on Tumor necrosis factor superfamily and post-translational modifications

Issue of 2020–05–31
fiveteen papers selected by
John Silke, Walter and Eliza Hall Institute of Medical Research

Differences in the sensitivity of classically and alternatively activated macrophages to TAK1 inhibitor-induced necroptosis.
Antibody RING-Mediated Destruction of Endogenous Proteins.
Heat shock response regulates stimulus-specificity and sensitivity of the pro-inflammatory NF-κB signalling.
HDAC3-ERα Selectively Regulates TNF-α-Induced Apoptotic Cell Death in MCF-7 Human Breast Cancer Cells via the p53 Signaling Pathway.
The LUBAC participates in lysophosphatidic acid-induced NF-κB activation.
Regulation of poly ADP-ribosylation of VEGF by an interplay between PARP-16 and TNKS-2.
Cell surface IL-1α trafficking is specifically inhibited by interferon-γ, and associates with the membrane via IL-1R2 and GPI anchors.
IL-23 in arthritic and inflammatory pain development in mice.
Identification of novel interacting partners of the NEDD4 ubiquitin ligase in mouse testis.
Recombinant programmed cell death 1 inhibits psoriatic inflammation in imiquimod‑treated mice.
Factors associated with citation of original articles in five high-impact factor dermatology journals.
Heat stress induces RIP1/RIP3-dependent necroptosis through the MAPK, NF-κB, and c-Jun signaling pathways in pulmonary vascular endothelial cells.
Targeting TDP-43 proteinopathy with drugs and drug-like small molecules.
Ubiquitin-like proteins in the DNA damage response: the next generation.
CXCR4 Signaling Has a CXCL12-Independent Essential Role in Murine MLL-AF9-Driven Acute Myeloid Leukemia.

Cancer Immunol Immunother. 2020 May 29.

Differences in the sensitivity of classically and alternatively activated macrophages to TAK1 inhibitor-induced necroptosis.

Zsófia Varga, Tamás Molnár, Anett Mázló, Ramóna Kovács, Viktória Jenei, Krisztina Kerekes, Attila Bácsi, Gábor Koncz.

  Controlling the balance of pro-inflammatory M1 versus anti-inflammatory M2 macrophages may have paramount therapeutic benefit in cardiovascular diseases, infections, cancer and chronic inflammation. The targeted depletion of different macrophage populations provides a therapeutic option to regulate macrophage-mediated functions. Macrophages are highly sensitive to necroptosis, a newly described regulated cell death mediated by receptor-interacting serine/threonine-protein kinase 1 (RIPK1), RIPK3 and mixed lineage kinase domain like pseudokinase. Antagonists of inhibitors of apoptosis proteins (SMAC mimetics) block RIPK1 ubiquitination, while TGF-activated kinase 1 (TAK1) inhibitors prevent the phosphorylation of RIPK1, resulting in increased necroptosis. We compared the sensitivity of monocyte-derived human M1 and M2 cells to various apoptotic and necroptotic signals. The two cell types were equally sensitive to all investigated stimuli, but TAK1 inhibitor induced more intense necroptosis in M2 cells. Consequently, the treatment of co-cultured M1 and M2 cells with TAK1 inhibitor shifted the balance of the two populations toward M1 dominance. Blockage of either Aurora Kinase A or glycogen synthase kinase 3β, two newly described necroptosis inhibitors, increased the sensitivity of M1 cells to TAK1-inhibitor-induced cell death. Finally, we demonstrated that in vitro differentiated tumor-associated macrophages (TAM-like cells) were as highly sensitive to TAK1 inhibitor-induced necroptosis as M2 cells. Our results indicate that at least two different necroptotic pathways operate in macrophages and the targeted elimination of different macrophage populations by TAK1 inhibitor or SMAC mimetic may provide a therapeutic option to regulate the balance of inflammatory/anti-inflammatory macrophage functions.

Keywords:  Cancer; Inflammation; Macrophage; Necroptosis

DOI:  https://doi.org/10.1007/s00262-020-02623-7
Mol Cell. 2020 May 14. pii: S1097-2765(20)30274-4. [Epub ahead of print]

Antibody RING-Mediated Destruction of Endogenous Proteins.

Adel F M Ibrahim, Linnan Shen, Michael H Tatham, David Dickerson, Alan R Prescott, Naima Abidi, Dimitris P Xirodimas, Ronald T Hay.

  To understand gene function, the encoding DNA or mRNA transcript can be manipulated and the consequences observed. However, these approaches do not have a direct effect on the protein product of the gene, which is either permanently abrogated or depleted at a rate defined by the half-life of the protein. We therefore developed a single-component system that could induce the rapid degradation of the specific endogenous protein itself. A construct combining the RING domain of ubiquitin E3 ligase RNF4 with a protein-specific camelid nanobody mediates target destruction by the ubiquitin proteasome system, a process we describe as antibody RING-mediated destruction (ARMeD). The technique is highly specific because we observed no off-target protein destruction. Furthermore, bacterially produced nanobody-RING fusion proteins electroporated into cells induce degradation of target within minutes. With increasing availability of protein-specific nanobodies, this method will allow rapid and specific degradation of a wide range of endogenous proteins.

Keywords:  ARMeD; E3 ligase; nanobody-RING fusion; proteasome; protein degradation; ubiquitin

DOI:  https://doi.org/10.1016/j.molcel.2020.04.032
Cell Commun Signal. 2020 May 24. 18(1): 77

Heat shock response regulates stimulus-specificity and sensitivity of the pro-inflammatory NF-κB signalling.

Anna Paszek, Małgorzata Kardyńska, James Bagnall, Jarosław Śmieja, David G Spiller, Piotr Widłak, Marek Kimmel, Wieslawa Widlak, Pawel Paszek.

   BACKGROUND: Ability to adapt to temperature changes trough the Heat Shock Response (HSR) pathways is one of the most fundamental and clinically relevant cellular response systems. Heat Shock (HS) affects the signalling and gene expression responses of the Nuclear Factor κB (NF-κB) transcription factor, a critical regulator of proliferation and inflammation, however, our quantitative understanding of how cells sense and adapt to temperature changes is limited.
METHODS: We used live-cell time-lapse microscopy and mathematical modelling to understand the signalling of the NF-κB system in the human MCF7 breast adenocarcinoma cells in response to pro-inflammatory Interleukin 1β (IL1β) and Tumour Necrosis Factor α (TNFα) cytokines, following exposure to a 37-43 °C range of physiological and clinical temperatures.
RESULTS: We show that exposure to 43 °C 1 h HS inhibits the immediate NF-κB signalling response to TNFα and IL1β stimulation although uptake of cytokines is not impaired. Within 4 h after HS treatment IL1β-induced NF-κB responses return to normal levels, but the recovery of the TNFα-induced responses is still affected. Using siRNA knock-down of Heat Shock Factor 1 (HSF1) we show that this stimulus-specificity is conferred via the Inhibitory κB kinase (IKK) signalosome where HSF1-dependent feedback regulates TNFα, but not IL1β-mediated IKK recovery post HS. Furthermore, we demonstrate that through the temperature-dependent denaturation and recovery of IKK, TNFα and IL1β-mediated signalling exhibit different temperature sensitivity and adaptation to repeated HS when exposed to a 37-43 °C temperature range. Specifically, IL1β-mediated NF-κB responses are more robust to temperature changes in comparison to those induced by TNFα treatment.
CONCLUSIONS: We demonstrate that the kinetics of the NF-κB system following temperature stress is cytokine specific and exhibit differential adaptation to temperature changes. We propose that this differential temperature sensitivity is mediated via the IKK signalosome, which acts as a bona fide temperature sensor trough the HSR cross-talk. This novel quantitative understanding of NF-κB and HSR interactions is fundamentally important for the potential optimization of therapeutic hyperthermia protocols. Video Abstract.

Keywords:  HSF1; Heat-shock; IKK signalosome; Live-cell imaging; Mathematical modelling; NF-kappaB signalling; Single-cell analyses

DOI:  https://doi.org/10.1186/s12964-020-00583-0
Cells. 2020 May 21. pii: E1280. [Epub ahead of print]9(5):

HDAC3-ERα Selectively Regulates TNF-α-Induced Apoptotic Cell Death in MCF-7 Human Breast Cancer Cells via the p53 Signaling Pathway.

Seung-Ho Park, Hyunhee Kim, Sungmin Kwak, Ji-Hoon Jeong, Jangho Lee, Jin-Taek Hwang, Hyo-Kyoung Choi, Kyung-Chul Choi.

  Tumor necrosis factor-α (TNF-α) plays a significant role in inflammation and cancer-related apoptosis. We identified a TNF-α-mediated epigenetic mechanism of apoptotic cell death regulation in estrogen receptor-α (ERα)-positive human breast cancer cells. To assess the apoptotic effect of TNF-α, annexin V/ propidium iodide (PI) double staining, cell viability assays, and Western blotting were performed. To elucidate this mechanism, histone deacetylase (HDAC) activity assay and immunoprecipitation (IP) were conducted; the mechanism was subsequently confirmed through chromatin IP (ChIP) assays. Finally, we assessed HDAC3-ERα-mediated apoptotic cell death after TNF-α treatment in ERα-positive human breast cancer (MCF-7) cells via the transcriptional activation of p53 target genes using luciferase assay and quantitative reverse transcription PCR. The TNF-α-induced selective apoptosis in MCF-7 cells was negatively regulated by the HDAC3-ERα complex in a caspase-7-dependent manner. HDAC3 possessed a p53-binding element, thus suppressing the transcriptional activity of its target genes. In contrast, MCF-7 cell treatment with TNF-α led to dissociation of the HDAC3-ERα complex and substitution of the occupancy on the promoter by the p53-p300 complex, thus accelerating p53 target gene expression. In this process, p53 stabilization was accompanied by its acetylation. This study showed that p53-mediated apoptosis in ERα-positive human breast cancer cells was negatively regulated by HDAC3-ERα in a caspase-7-dependent manner. Therefore, these proteins have potential application in therapeutic strategies.

Keywords:  ERα; HDAC3; TNF-α; apoptosis; p53

DOI:  https://doi.org/10.3390/cells9051280
Cell Immunol. 2020 May 18. pii: S0008-8749(20)30190-8. [Epub ahead of print]353 104133

The LUBAC participates in lysophosphatidic acid-induced NF-κB activation.

Tiphaine Douanne, Sarah Chapelier, Robert Rottapel, Julie Gavard, Nicolas Bidère.

  The natural bioactive glycerophospholipid lysophosphatidic acid (LPA) binds to its cognate G protein-coupled receptors (GPCRs) on the cell surface to promote the activation of several transcription factors, including NF-κB. LPA-mediated activation of NF-κB relies on the formation of a signalosome that contains the scaffold CARMA3, the adaptor BCL10 and the paracaspase MALT1 (CBM complex). The CBM complex has been extensively studied in lymphocytes, where it links antigen receptors to NF-κB activation via the recruitment of the linear ubiquitin assembly complex (LUBAC), a tripartite complex of HOIP, HOIL1 and SHARPIN. Moreover, MALT1 cleaves the LUBAC subunit HOIL1 to further enhance NF-κB activation. However, the contribution of the LUBAC downstream of GPCRs has not been investigated. By using murine embryonic fibroblasts from mice deficient for HOIP, HOIL1 and SHARPIN, we report that the LUBAC is crucial for the activation of NF-κB in response to LPA. Further echoing the situation in lymphocytes, LPA unbridles the protease activity of MALT1, which cleaves HOIL1 at the Arginine 165. The expression of a MALT1-insensitive version of HOIL1 reveals that this processing is involved in the optimal production of the NF-κB target cytokine interleukin-6. Lastly, we provide evidence that the guanine exchange factor GEF-H1 favors MALT1-mediated cleavage of HOIL1 and NF-κB signaling in this context. Together, our results unveil a critical role for the LUBAC as a positive regulator of NF-κB signaling downstream of LPA receptors.

Keywords:  CBM complex; GEF-H1; LPA; LUBAC; MALT1; NF-κB

DOI:  https://doi.org/10.1016/j.cellimm.2020.104133
Mol Cell Biochem. 2020 May 30.

Regulation of poly ADP-ribosylation of VEGF by an interplay between PARP-16 and TNKS-2.

Haritha Kunhiraman, Vishnu Ramachandran, Lincy Edatt, V B Sameer Kumar.

  The biological activity of vascular endothelial growth factor (VEGF), the major cytokine regulating the process of angiogenesis is tightly controlled at multiple levels including processes involving post-translational modification such as ADP-ribosylation and glycosylation. ADP-ribosylation is a reversible NAD+-dependent modification, catalyzed by poly ADP-ribose polymerase (PARP) or ADP-ribosyl transferase (ADPRTs) and has been reported by us and others as a modification that reduces the biological activity of VEGF. The factors responsible for any such modification should occur in the secretory pathway, i.e., in the endoplasmic reticulum and Golgi. Our investigation carried out in this direction revealed that ADP-ribosylation of VEGF requires the interplay between members of poly ADP-ribose polymerase (PARP) family in the secretory pathway, viz., ER associated PARP-16 and Golgi associated Tankyrase-2 (TNKS-2). The data presented in this manuscript suggest that PARP-16 catalysis the priming mono ADP-ribosylation of VEGF which is a prerequisite for poly ADP-ribosylation of VEGF by TNKS-2.

Keywords:  ADP-ribosylation; Angiogenesis; PARP-16; TNKS-2; VEGF

DOI:  https://doi.org/10.1007/s11010-020-03746-2
Eur J Immunol. 2020 May 24.

Cell surface IL-1α trafficking is specifically inhibited by interferon-γ, and associates with the membrane via IL-1R2 and GPI anchors.

Julie Ne Chan, Melanie Humphry, Lauren Kitt, Dominika Krzyzanska, Kara J Filbey, Martin R Bennett, Murray Ch Clarke.

  Interleukin-1 (IL-1) is a powerful cytokine that drives inflammation and modulates adaptive immunity. Both IL-1α and IL-1β are translated as proforms that require cleavage for full cytokine activity and release, while IL-1α is reported to occur as an alternative plasma membrane-associated form on many cell types. However, the existence of cell surface IL-1α (csIL-1α) is contested, how IL-1α tethers to the membrane is unknown, and signalling pathways controlling trafficking are not specified. Using a robust and fully validated system we show that macrophages present bona fide csIL-1α after ligation of toll-like receptors. Pro-IL-1α tethers to the plasma membrane in part through IL-1R2 or via association with a Glycosylphosphatidylinositol-anchored protein, and can be cleaved, activated and released by proteases. csIL-1α requires de novo protein synthesis and its trafficking to the plasma membrane is exquisitely sensitive to inhibition by interferon γ, independent of expression level. We also reveal how prior csIL-1α detection could occur through inadvertent cell permeabilisation, and that senescent cells do not drive the senescent-associated secretory phenotype via csIL-1α, but rather via soluble IL-1α. We believe this data is important for determining the local or systemic context in which IL-1α can contribute to disease and/or physiological processes. This article is protected by copyright. All rights reserved.

Keywords:  IL-1; inflammation; innate immunity; interferon; macrophage

DOI:  https://doi.org/10.1002/eji.201948521
Arthritis Res Ther. 2020 May 29. 22(1): 123

IL-23 in arthritic and inflammatory pain development in mice.

Kevin M-C Lee, Zihao Zhang, Adrian Achuthan, Andrew J Fleetwood, Julia E Smith, John A Hamilton, Andrew D Cook.

   BACKGROUND: The cytokine, interleukin-23 (IL-23), can be critical for the progression of inflammatory diseases, including arthritis, and is often associated with T lymphocyte biology. We previously showed that certain lymphocyte-independent, inflammatory arthritis and pain models have a similar requirement for tumour necrosis factor (TNF), granulocyte macrophage-colony stimulating factor (GM-CSF), and C-C motif ligand 17 (CCL17). Given this correlation in cytokine requirements, we explored whether IL-23 might interact with this cytokine cluster in the control of arthritic and inflammatory pain.
METHODS: The role of IL-23 in the development of pain-like behaviour was investigated using mouse arthritis models (zymosan-induced arthritis and GM-CSF-, TNF-, and CCL17-driven monoarticular arthritis) and inflammatory pain models (intraplantar zymosan, GM-CSF, TNF, and CCL17). Additionally, IL-23-induced inflammatory pain was measured in GM-CSF-/-, Tnf-/-, and Ccl17E/E mice and in the presence of indomethacin. Pain-like behaviour and arthritis were assessed by relative weight distribution in hindlimbs and histology, respectively. Cytokine mRNA expression in knees and paw skin was analysed by quantitative PCR. Blood and synovial cell populations were analysed by flow cytometry.
RESULTS: We report, using Il23p19-/- mice, that innate immune (zymosan)-driven arthritic pain-like behaviour (herein referred to as pain) was completely dependent upon IL-23; optimal arthritic disease development required IL-23 (P < 0.05). Zymosan-induced inflammatory pain was also completely dependent on IL-23. In addition, we found that exogenous TNF-, GM-CSF-, and CCL17-driven arthritic pain, as well as inflammatory pain driven by each of these cytokines, were absent in Il23p19-/- mice; optimal disease in these mBSA-primed models was dependent on IL-23 (P < 0.05). Supporting this cytokine connection, it was found conversely that IL-23 (200 ng) can induce inflammatory pain at 4 h (P < 0.0001) with a requirement for each of the other cytokines as well as cyclooxygenase activity.
CONCLUSIONS: These findings indicate a role for IL-23 in innate immune-mediated arthritic and inflammatory pain with potential links to TNF, GM-CSF, CCL17, and eicosanoid function.

Keywords:  Arthritis; CCL17; GM-CSF; IL-23; Pain; TNF

DOI:  https://doi.org/10.1186/s13075-020-02212-0
J Proteomics. 2020 May 22. pii: S1874-3919(20)30198-6. [Epub ahead of print]223 103830

Identification of novel interacting partners of the NEDD4 ubiquitin ligase in mouse testis.

JantinaA Manning, Simon P Windley, Jarrod J Sandow, Sonia S Shah, Patrick Western, Dagmar Wilhelm, Sharad Kumar.

  Posttranslational modification by ubiquitination targets proteins for degradation, recycling, stabilization or altered trafficking, and as such can alter cellular signaling pathways. The substrate specificity of this multistep process is controlled by ubiquitin ligases, including those of the HECT domain-containing NEDD4 family. In the testis, ubiquitination of many proteins contributes to organ development and maturation of spermatozoa and NEDD4 is known to be important in the control of spermatogonial stem cell homeostasis. However, a comprehensive understanding of NEDD4 substrates in testis development is lacking. Here we demonstrate high expression of Nedd4 in somatic cells of the mouse testis and in the murine Leydig cell-like cell line TM3. Immunoprecipitation of NEDD4 tagged with GFP at either the amino or carboxyl terminus was subjected to proteomic analysis for interacting proteins. We identified a substantial list of potential interaction partners, including known NEDD4 substrates, proteins involved in ubiquitination and proteins important for testis development and spermatogenesis. We confirmed the interaction of NEDD4 with a subset of these putative interacting proteins, validating the integrity of the dataset. These potential interactors may be further explored to reveal important roles of NEDD4-mediated ubiquitination in the testis. SIGNIFICANCE: Ubiquitination is important for testis development and function, and NEDD4 is known to ubiquitinate various proteins to affect cellular signaling and development, including those implicated in spermatogenesis. However, substrates of NEDD4 that are important during testis development remain to be identified. Here we report NEDD4 expression in the developing testis and TM3 testicular cell line. This study identifies a substantial list of NEDD4 interacting proteins in the TM3 testicular cell line, with validation of some of these interactions. Hence, this provides novel NEDD4 targets that may contribute to testis development and function that may be further explored.

Keywords:  Immunoprecipitation; NEDD4; Testis development

DOI:  https://doi.org/10.1016/j.jprot.2020.103830
Int J Mol Med. 2020 May 21.

Recombinant programmed cell death 1 inhibits psoriatic inflammation in imiquimod‑treated mice.

Shiguang Peng, Mei Cao, Xiaoying Sun, Yaqiong Zhou, Chu-Yen Chen, Tian Ma, Hongjin Li, Bin Li, Bo Zhu, Xin Li.

Psoriasis is a common chronic inflammatory skin disease. Programmed cell death ligand 1 (PD‑L1) and programmed cell death 1 (PD‑1) are expressed on immune cells in a number of chronic inflammatory diseases. However, a limited number of studies have investigated the expression and function of the PD‑L1 and PD‑1 pathway in psoriatic inflammation. The present study used human psoriasis samples and imiquimod‑induced murine psoriasis models to investigate the potential role of PD‑1 in the modulation of psoriatic inflammation. The results demonstrated that inhibition of PD‑1 function with antibodies promoted psoriasis development. PD‑1‑fragment crystallizable (PD‑1‑Fc) treatment inhibited psoriatic inflammation and exhibited additive effects with anti‑tumor necrosis factor α therapy in imiquimod‑induced mouse psoriasis, suggesting that PD‑1‑Fc treatment may serve as a new therapeutic strategy for psoriasis.

DOI: https://doi.org/10.3892/ijmm.2020.4612
J Am Acad Dermatol. 2020 May 21. pii: S0190-9622(20)30944-0. [Epub ahead of print]

Factors associated with citation of original articles in five high-impact factor dermatology journals.

Marius Mølsted Flege, Simon Francis Thomsen.

DOI: https://doi.org/10.1016/j.jaad.2020.05.075
Biochem Biophys Res Commun. 2020 May 26. pii: S0006-291X(20)30890-1. [Epub ahead of print]

Heat stress induces RIP1/RIP3-dependent necroptosis through the MAPK, NF-κB, and c-Jun signaling pathways in pulmonary vascular endothelial cells.

Wei Huang, Weidang Xie, Jian Gong, Wenyan Wang, Sumin Cai, Qiaobing Huang, Zhongqing Chen, Yanan Liu.

  Necroptosis represents a newly defined form of regulated necrosis and participates in various human inflammatory diseases. It remains unclear whether necroptosis is presented in heatstroke-induced lung injury. We show that heat stress(HS) triggered an significant upregulation of receptor-interacting protein 1 (RIP1) and mixed lineage kinase domain-like protein (MLKL) expression in a time-dependent manner, without a significant change of receptor-interacting protein 3 (RIP3). Furthermore, co-immunoprecipitation assays showed that RIP1 binds to RIP3 to form the necrosome in heat stress-induced PMVECs. In vitro, necrostatin-1 (Nec-1) pre-treatment reduced heat stress-induced PMVECs necroptosis, which also inhibited HMGB1 translocation from the nucleus into the cytoplasm. Similarly, inhibition for ERK (PD98059), NF-κB (BAY11-7082) and c-Jun (c-Jun peptide), respectively, also suppressed the HMGB1 cytoplasm translocation. Furthermore, siRNA-mediated RIP1/RIP3 knockdown negatively regulated the release of HMGB1 in HS-induced necroptosis through the ERK, NF-κB, and c-Jun signaling pathways. Our study reveals that HS induces RIP1/RIP3-dependent necroptosis through the MAPK, NF-κB, and c-Jun signaling pathways in PMVECs.

Keywords:  Heat stress; MAPKs; NF-κB; Necroptosis; PMVECs; c-Jun

DOI:  https://doi.org/10.1016/j.bbrc.2020.04.150
Br J Pharmacol. 2020 May 29.

Targeting TDP-43 proteinopathy with drugs and drug-like small molecules.

Emanuele Buratti.

Following the discovery of TDP-43 involvement in Amyotrophic Lateral Sclerosis (ALS) and Frontotemporal Lobar Degeneration (FTLD) a major research focus has been to develop treatments that can prevent or alleviate disease conditions. From a pharmacological point of view, one approach has been to use TDP-43 based disease-models to test small molecules and drugs already known to have some therapeutic effect in a variety of neurodegenerative conditions. In parallel, various disease models have been used to perform high-throughput screens of drugs and small compound libraries. The aim of this review will be to provide a general overview of the compounds that have been described to alter pathological characteristics of TDP-43. These include expression levels, cytoplasmic mislocalization, post-translational modifications, cleavage, stress granule recruitment, and aggregation. In parallel, this review will also address the use of compounds that modify the autophagic/proteasome systems that are known to target TDP-43 misfolding and aggregation.

DOI: https://doi.org/10.1111/bph.15148
Essays Biochem. 2020 May 26. pii: EBC20190095. [Epub ahead of print]

Ubiquitin-like proteins in the DNA damage response: the next generation.

Isabelle C Da Costa, Christine K Schmidt.

  DNA suffers constant insult from a variety of endogenous and exogenous sources. To deal with the arising lesions, cells have evolved complex and coordinated pathways, collectively termed the DNA damage response (DDR). Importantly, an improper DDR can lead to genome instability, premature ageing and human diseases, including cancer as well as neurodegenerative disorders. As a crucial process for cell survival, regulation of the DDR is multi-layered and includes several post-translational modifications. Since the discovery of ubiquitin in 1975 and the ubiquitylation cascade in the early 1980s, a number of ubiquitin-like proteins (UBLs) have been identified as post-translational modifiers. However, while the importance of ubiquitin and the UBLs SUMO and NEDD8 in DNA damage repair and signalling is well established, the roles of the remaining UBLs in the DDR are only starting to be uncovered. Herein, we revise the current status of the UBLs ISG15, UBL5, FAT10 and UFM1 as emerging co-regulators of DDR processes. In fact, it is becoming clear that these post-translational modifiers play important pleiotropic roles in DNA damage and/or associated stress-related cellular responses. Expanding our understanding of the molecular mechanisms underlying these emerging UBL functions will be fundamental for enhancing our knowledge of the DDR and potentially provide new therapeutic strategies for various human diseases including cancer.

Keywords:  DNA damage response (DDR); DNA repair; FAT10; ISG15; UBL5; UFM1; Ubiquitin-like proteins (UBLs)

DOI:  https://doi.org/10.1042/EBC20190095
Cell Rep. 2020 May 26. pii: S2211-1247(20)30637-9. [Epub ahead of print]31(8): 107684

CXCR4 Signaling Has a CXCL12-Independent Essential Role in Murine MLL-AF9-Driven Acute Myeloid Leukemia.

Ramprasad Ramakrishnan, Pablo Peña-Martínez, Puneet Agarwal, Maria Rodriguez-Zabala, Marion Chapellier, Carl Högberg, Mia Eriksson, David Yudovich, Mansi Shah, Mats Ehinger, Björn Nilsson, Jonas Larsson, Anna Hagström-Andersson, Benjamin L Ebert, Ravi Bhatia, Marcus Järås.

  Acute myeloid leukemia (AML) is defined by an accumulation of immature myeloid blasts in the bone marrow. To identify key dependencies of AML stem cells in vivo, here we use a CRISPR-Cas9 screen targeting cell surface genes in a syngeneic MLL-AF9 AML mouse model and show that CXCR4 is a top cell surface regulator of AML cell growth and survival. Deletion of Cxcr4 in AML cells eradicates leukemia cells in vivo without impairing their homing to the bone marrow. In contrast, the CXCR4 ligand CXCL12 is dispensable for leukemia development in recipient mice. Moreover, expression of mutated Cxcr4 variants reveals that CXCR4 signaling is essential for leukemia cells. Notably, loss of CXCR4 signaling in leukemia cells leads to oxidative stress and differentiation in vivo. Taken together, our results identify CXCR4 signaling as essential for AML stem cells by protecting them from differentiation independent of CXCL12 stimulation.

Keywords:  CRISPR; CXCL12; CXCR4; CXCR4 signaling; ROS; acute myeloid leukemia; differentiation; leukemia stem cell; oxidative stress; screen

DOI:  https://doi.org/10.1016/j.celrep.2020.107684